The present invention relates to an automatic cycle control for a surface grinding machine in which grinding wheel attrition caused by grinding and dressing operations are automatically compensated for and used to adjust subsequent grinding and dressing cycles.
Surface grinding machines in which the face of a grinding wheel is advanced into forceful engagement with a workpiece are well known in the art. The grinding operation which removes stock material from the workpiece also necessarily wears down the abrasive surface of the grinding disc. In precision grinding operations this loss of the grinding disc material must be taken into account when advancing the discs into the workpiece in order to insure that consecutive workpieces will be finish ground to the same size. This compensation requires constant intervention by a machine operator; or in the past, has been performed by assuming a fractional loss of the grinding disc with each grinding operation and adjusting the infeed of the grinding disc accordingly. Such assumptions are not always completely accurate and consequently require periodic workpiece sizing and further compensation of the grinding machine cycle.
In order to maintain the desired flat profile of the grinding disc when grinding successive workpieces, periodic dressing operations are performed in which a diamond tool is used to dress the face of the disc. This dressing operation is time consuming since the disc has to be accurately positioned with respect to the diamond dressing tool in order to obtain a satisfactory dress. Subsequent grinding operations require an adjustment of the infeed control of the disc assemblies since the thickness of the grinding disc measured in the direction of the grinding disc infeed is reduced.
Consecutive grinding cycle parameters may be controlled by a program which relies on assumed relationships, but such control is not completely accurate because of variations in grinding disc and workpiece physical characteristics. If the grinding disc wears faster than anticipated, the result may be a number of finish ground workpieces which are oversized. If the grinding discs do not wear as quickly as anticipated, the infeed control of the oversized discs can result in workpieces being finished undersize, or the tooling which holds the workpiece being ground by the grinding wheel.